Display device and method of manufacturing the same

ABSTRACT

A display device including: a first substrate; first through third subpixel electrodes which are disposed on the first substrate to neighbor each other; a second substrate opposing the first substrate; a first wavelength conversion pattern at least partially overlapping the first subpixel electrode and a second wavelength conversion pattern at least partially overlapping the second subpixel electrode; a first light transmission pattern at least partially overlapping the third subpixel electrode and a second light transmission pattern disposed between the first wavelength conversion pattern and the second wavelength conversion pattern; and a low refractive layer which has a lower refractive index than the first and second wavelength conversion patterns.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. patent application Ser. No.15/883,064, filed on Jan. 29, 2018, and claims priority from and thebenefit of Korean Patent Application No. 10-2017-0112734, filed on Sep.4, 2017, which is hereby incorporated by reference for all purposes asif fully set forth herein.

BACKGROUND Field

Exemplary embodiments relate to a display device and a method ofmanufacturing the same.

Discussion of the Background

With the development of multimedia, display devices are becomingincreasingly important. Accordingly, various types of display devicessuch as liquid crystal displays (LCDs) and organic light-emittingdisplays (OLEDs) are being used.

Of these display devices, LCDs are one of the most widely used types offlat panel displays. An LCD includes a pair of substrates having fieldgenerating electrodes, such as pixel electrodes and a common electrode,and a liquid crystal layer interposed between the two substrates. In theLCD, voltages are applied to the field generating electrodes to generatean electric field in the liquid crystal layer. Accordingly, thealignment of liquid crystal molecules of the liquid crystal layer isdetermined, and the polarization of incident light is controlled. As aresult, a desired image is displayed on the LCD.

As one way to make each pixel uniquely display one primary color, acolor conversion pattern may be placed in each pixel on an optical pathextending from a light source to a viewer. For example, a color filtermay realize a primary color by transmitting only a specific wavelengthband.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the inventive concept,and, therefore, it may contain information that does not form the priorart that is already known in this country to a person of ordinary skillin the art.

SUMMARY

Exemplary embodiments provide a display device which can improve lightoutput efficiency by including a low refractive layer and a method ofmanufacturing the display device.

Exemplary embodiments provide a display device which provides flatnessto a low refractive layer and a planarization layer by placing a lighttransmission pattern in a valley area between wavelength conversionpatterns and a method of manufacturing the display device.

Additional aspects will be set forth in the detailed description whichfollows, and, in part, will be apparent from the disclosure, or may belearned by practice of the inventive concept.

According to exemplary embodiments, a display device comprises: a firstsubstrate; first through third subpixel electrodes which are disposed onthe first substrate to neighbor each other; a second substrate which isopposite the first substrate; wavelength conversion patterns which aredisposed on the second substrate and comprise a first wavelengthconversion pattern at least partially overlapping the first subpixelelectrode and a second wavelength conversion pattern at least partiallyoverlapping the second subpixel electrode; light transmission patternswhich comprise a first light transmission pattern at least partiallyoverlapping the third subpixel electrode and a second light transmissionpattern disposed between the first wavelength conversion pattern and thesecond wavelength conversion pattern; a planarization layer which isdisposed on the wavelength conversion patterns and the lighttransmission patterns; and a low refractive layer which has a lowerrefractive index than the wavelength conversion patterns. The lowrefractive layer may comprise at least one of a first low refractivelayer disposed between the wavelength conversion patterns and the secondsubstrate and a second low refractive layer disposed between thewavelength conversion patterns and the planarization layer.

According to exemplary embodiments, a display device comprises: abacklight unit which emits light displaying a first color; and a displaypanel which receives the light displaying the first color. The displaypanel nay comprise: a substrate; wavelength conversion patterns whichare disposed on the substrate and comprise a first wavelength conversionpattern converting the light displaying the first color into lightdisplaying a second color different from the first color and a secondwavelength conversion pattern converting the light displaying thy: firstcolor into light displaying a third color different from the firstcolor; light transmission patterns which comprise a first lighttransmission pattern transmitting the light displaying the first colorand a second light transmission pattern disposed between the firstwavelength conversion pattern and the second wavelength conversionpattern; and a low refractive layer which has a lower refractive indexthan the wavelength conversion patterns. The low refractive layer maycomprise at least one of a first low refractive layer disposed betweenthe wavelength conversion patterns and the substrate and a second lowrefractive layer disposed on the wavelength conversion patterns.

According to exemplary embodiments, a method of manufacturing a displaydevice comprises: forming a first low refractive layer on a substrate;forming wavelength conversion patterns, which comprise a firstwavelength conversion pattern converting light having a first wavelengthband into light having a second wavelength band and a second wavelengthconversion pattern converting the light having the first wavelength bandinto light having a third wavelength band, on the first low refractivelayer; forming light transmission patterns which comprise a first lighttransmission pattern transmitting the light having the first wavelengthband and a second light transmission pattern disposed between the firstwavelength conversion pattern and the second wavelength conversionpattern; and forming a second low refractive layer on the wavelengthconversion patterns and the light transmission patterns. Refractiveindices of the first low refractive layer and the second low refractivelayer may be lower than those of the wavelength conversion patterns.

The foregoing general description and the following detailed descriptionare exemplary and explanatory and are intended to provide furtherexplanation of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the inventive concept, and are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments of the inventive concept, and, together with thedescription, serve to explain principles of the inventive concept.

FIG. 1 is a cross-sectional view of a display device according to anembodiment;

FIG. 2 is a schematic view of a first subpixel illustrated in FIG. 1;

FIG. 3 is an enlarged view of an area A illustrated in FIG. 1;

FIGS. 4A through 5B illustrate optical paths in the display deviceaccording to the embodiment;

FIG. 6A illustrates the area A of FIG. 1 turned over;

FIG. 6B illustrates the area A of FIG. 1 turned over in a case where asecond light transmission pattern is omitted;

FIG. 7 illustrates the flatness of a surface of a planarization layeramong elements of the display device according to the embodiment;

FIG. 8 is a view for explaining the color mixing reducing effect of thedisplay device according to the embodiment;

FIGS. 9 through 14 illustrate other embodiments of the display device ofFIG. 1;

FIG. 15 is a graph illustrating the luminance according to the positionof a low refractive layer in a display device according to anembodiment;

FIG. 16 illustrates an embodiment of the display device of FIG. 1; and

FIGS. 17 through 22 illustrate a method of manufacturing a displaydevice according to an embodiment.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments. It is apparent, however,that various exemplary embodiments may be practiced without thesespecific details or with one or more equivalent arrangements. In otherinstances, well-known structures and devices are shown in block diagramform in order to avoid unnecessarily obscuring various exemplaryembodiments.

In the accompanying figures, the size and relative sizes of layers,films, panels, regions, etc., may be exaggerated for clarity anddescriptive purposes. Also, like reference numerals denote likeelements.

When an element or layer is referred to as being “on,” “connected to,”or “coupled to” another element or layer, it may be directly on,connected to, or coupled to the other element or layer or interveningelements or layers may be present. When, however, an element or layer isreferred to as being “directly on,” “directly connected to,” or“directly coupled to” another element or layer, there are no interveningelements or layers present. For the purposes of this disclosure, “atleast one of X, Y, and Z” and “at least one selected from the groupconsisting of X, Y, and Z” may be construed as X only, Y only, Z only,or any combination of two or more of X, Y, and Z, such as, for instance,XYZ, XYY, YZ, and ZZ. Like numbers refer to like elements throughout. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

Although the terms first, second, etc. may be used herein to describevarious elements, components, regions, layers, and/or sections, theseelements, components, regions, layers, and/or sections should not belimited by these terms. These terms are used to distinguish one element,component, region, layer, and/or section from another element,component, region, layer, and/or section. Thus, a first element,component, region, layer, and/or section discussed below could be termeda second element, component, region, layer, and/or section withoutdeparting from the teachings of the present disclosure.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, may be used herein for descriptive purposes, and,thereby, to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the drawings. Spatiallyrelative terms are intended to encompass different orientations of anapparatus in use, operation, and/or manufacture in addition to theorientation depicted in the drawings. For example, if the apparatus inthe drawings is turned over, elements described as “below” or “beneath”other elements or features would then be oriented “above” the otherelements or features. Thus, the exemplary term “below” can encompassboth an orientation of above and below. Furthermore, the apparatus maybe otherwise oriented (e.g., rotated 90 degrees or at otherorientations), and, as such, the spatially relative descriptors usedherein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof.

Various exemplary embodiments are described herein with reference tosectional illustrations that are schematic illustrations of idealizedexemplary embodiments and/or intermediate structures. As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should not beconstrued as limited to the particular illustrated shapes of regions,but are to include deviations in shapes that result from, for instance,manufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the drawings are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and will not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

Hereinafter, exemplary embodiments rill be described with reference tothe accompanying drawings.

FIG. 1 is a cross-sectional view of a display device 1 according to anembodiment.

Referring to FIG. 1, the display device 1 according to the embodimentincludes a display panel 10 and a backlight unit 20.

The display panel 10 displays an image. The display panel 10 may includea lower display panel 100, an upper display panel 200, and a liquidcrystal layer 300. Here, the terms ‘lower’ and ‘upper’ are used for easeof description and are based on FIG. 1. The lower display panel 100 maybe placed to face the upper display panel 200. The liquid crystal layer300 may be interposed between the lower display panel 100 and the upperdisplay panel 200 and may include a plurality of liquid crystalmolecules 310. In an embodiment, the lower display panel 100 may bebonded to the upper display panel 200 by sealing.

The backlight unit 20 provides light to the display panel 10. Morespecifically, the backlight unit 20 may be disposed under the displaypanel 10 to provide light having a specific wavelength band to thedisplay panel 10. Hereinafter, light provided from the backlight unit 20to the display panel 10 will be referred to as light L1 having a firstwavelength band.

The backlight unit 20 may emit the light L1 having the first wavelengthband to the display panel 10. Here, the light L1 having the firstwavelength band is defined as light displaying a first color. The firstcolor may be blue having a center wavelength of about 420 to 480 nm inan embodiment. The center wavelength can also be expressed as a peakwavelength. That is, the light L1 having the first wavelength band isalso defined as blue light whose center wavelength is in the range ofabout 420 to 480 nm. Therefore, the backlight unit 20 can provide bluelight to the display panel 10. The display panel 10 is disposed on thepath of the light L1 having the first wavelength band emitted from thebacklight unit 20 and displays an image based on received light. Thearrangement relationship between the display panel 10 and the backlightunit 20 is not limited to that illustrated in FIG. 1 as long as thedisplay panel 10 is disposed on the path of light emitted from thebacklight unit 20.

The backlight unit 20 may include a light source which emits the abovelight and a light guide plate which guides the light received from thelight source to the display panel 10. The type of the light source isnot particularly limited. The light source may include a light emittingdiode (LED) or a laser diode (LD) in an embodiment. In addition, thematerial of the light guide plate is not particularly limited. The lightguide plate may be made of glass, quartz, or a plastic material such aspolyethylene terephthalate or polycarbonate in an embodiment.

Although not illustrated in the drawing, the backlight unit 20 mayinclude at least one optical sheet. The optical sheet may include atleast one of a prism sheet, a diffusion sheet, a lenticular lens sheet,and a micro lens sheet. The optical sheet can improve the displayquality of the display device 1 by modulating optical characteristics oflight emitted from the backlight unit 20, such as condensing, diffusion,scattering, or polarization characteristics.

The lower display panel 100, the upper display panel 200 and the liquidcrystal layer 300 will hereinafter be described in more detail.

First, the lower display panel 100 will be described. The lower displaypanel 100 may include a lower substrate 110, a first polarizing layer120, a plurality of pixels including a first pixel PX1, a firstinsulating layer 130, and a lower alignment film 140.

The lower substrate 110 may be a transparent insulating substrate in anembodiment. Here, the transparent insulating substrate may include aglass material, a quartz material, or a translucent plastic material.The lower substrate 110 may have flexibility in an embodiment.

The first polarizing layer 120 may be disposed on an optical pathbetween the lower substrate 110 and the backlight unit 20. In anembodiment, the first polarizing layer 120 may be disposed under thelower substrate 110. However, the position of the first polarizing layer120 is not limited to that illustrated in FIG. 1. In an embodiment, thefirst polarizing layer 120 may be disposed between the lower substrate110 and the liquid crystal layer 300. The first polarizing layer 120 maybe a reflective polarizing layer in an embodiment. When the firstpolarizing layer 120 is a reflective polarizing layer, it may transmit apolarization component parallel to a transmission axis and reflect apolarization component parallel to a reflection axis.

The first polarizing layer 120 may be in direct contact with the lowersubstrate 110 in an embodiment. That is, the first polarizing layer 120may be formed on a surface of the lower substrate 110 through acontinuous process.

In an embodiment, the first polarizing layer 120 may be bonded to thesurface of the lower substrate 110 by an adhesive member. Here, theadhesive member may be a pressure sensitive adhesive member (PSA) or anoptically clear adhesive member (OCA, OCR) in an embodiment.

The pixels including the first pixel PX1 may be disposed on the lowersubstrate 110. The pixels will hereinafter be described based on thefirst pixel PX1.

The first pixel PX1 may include first through third subpixels SPX1through SPX3. Here, the first through third subpixels SPX1 through SPX3display different colors. Each of the first through third subpixels SPX1through SPX3 includes a switching element and a subpixel electrode. Thiswill be described based on the first subpixel SPX1 by referring to FIG.2.

FIG. 2 is a schematic view of the first subpixel SPX1 illustrated inFIG. 1.

Referring to FIGS. 1 and 2, a first switching element Q1 may be athree-terminal element such as a thin-film transistor in an embodiment.The first switching element Q1 may have a control electrode electricallyconnected to a first scan line GL1 and have one electrode electricallyconnected to a first data line DL1. The other electrode of the firstswitching element Q1 may be electrically connected to a first subpixelelectrode SPE1. The first scan line GL1 may extend in a first directiond1 in an embodiment. The first data line DL1 may extend in a seconddirection d2, which is different from the first direction d1, in anembodiment. The first direction d1 intersects the second direction d2.

The first switching element Q1 may be turned on by a scan signalreceived from the first scan line GL1 to provide a data signal receivedfrom the first data line DL1 to the first subpixel electrode SPE1. Inthe present specification, the first subpixel SPX1 includes only onefirst switching element Q1. However, the inventive concept is notlimited to this case, and two or more switching elements can beincluded.

The first subpixel electrode SPE1 may be disposed in the lower displaypanel 100. More specifically, the first subpixel electrode SPE1 may bedisposed on the first insulating layer 130 located on the lowersubstrate 110. A common electrode CE may be located in the upper displaypanel 200 to be described later. The first subpixel electrode SPE1 maybe overlapped by at least part of the common electrode CE. Therefore,the first subpixel SPX1 may further include a first liquid crystalcapacitor Clc1 formed by the overlap of the first subpixel electrodeSPE1 and the common electrode CE. In the present specification, when‘two elements overlap each other,’ it means that the two elementsoverlap in a direction perpendicular to the lower substrate 110, unlessotherwise specified.

Referring again to FIG. 1, the first insulating layer 130 may bedisposed on the first through third switching elements Q1 through Q3.The first insulating layer 130 electrically insulates elements disposedunder the first insulating layer 130 from elements disposed on the firstinsulating layer 130.

In an embodiment, the first insulating layer 130 may be made of aninorganic material such as silicon nitride or silicon oxide. In anembodiment, the first insulating layer 130 may include an organicmaterial having an excellent planarization property and havingphotosensitivity. In an embodiment, the first insulating layer 130 maybe formed as a stacked structure of a layer made of an organic materialand a layer made of an inorganic material. The first insulating layer130 may include a plurality of contact holes for electrically connectingthe first through third switching elements Q1 through Q3 to the firstthrough third subpixel electrodes SPE1 through SPE3, respectively.

The first through third subpixel electrodes SPE1 through SPE3 may bedisposed on the first insulating layer 130 to neighbor each other. Eachof the first through third subpixel electrodes SPE1 through SPE3 may bea transparent electrode or a translucent electrode or may be made of areflective metal such as aluminum, silver, chromium or an alloy of thesematerials. Here, the transparent electrode or the translucent electrodemay include one or more of indium tin oxide (ITO), indium zinc oxide(IZO), zinc oxide (ZnO), indium oxide (In₂O₃), indium gallium oxide(IGO), and aluminum zinc oxide (AZO). Although not illustrated in thedrawing, each of the first through third subpixel electrodes SPE1through SPE3 may include a plurality of slits.

The lower alignment film 140 may be disposed on the first through thirdsubpixel electrodes SPE1 through SPE3. The lower alignment film 140 mayinduce the initial alignment of the liquid crystal molecules 310 in theliquid crystal layer 300. The lower alignment film 140 may include apolymer organic material having an imide group in a repeating unit of amain chain in an embodiment.

Next, the upper display panel 200 will be described. The upper displaypanel 200 may include an upper substrate 210, a black matrix BM,wavelength conversion patterns WC, light transmission patterns TC, afirst filter 220, a first low refractive layer 230, a second filter 240,a second low refractive layer 250, a planarization layer 260, a secondinsulating layer 270, a second polarizing layer 280, the commonelectrode CE, and an upper alignment film 290.

The upper substrate 210 is placed to face the lower substrate 110. Theupper substrate 210 may be made of transparent glass or plastic. In anembodiment, the upper substrate 210 may be made of the same material asthe lower substrate 110.

The black matrix BM may be disposed on the upper substrate 210. Theblack matrix BM is disposed at boundaries between the pixels andprevents transmission of light, thereby preventing color mixing betweenneighboring pixels. Based on FIG. 1, the black matrix BM is disposed atthe boundaries between the first through third subpixels SPX1 throughSPX3. The material of the black matrix BM is not particularly limited aslong as it can block the transmission of light provided to the blackmatrix BM. In an embodiment, the black matrix BM may include an organicmaterial or a metal material such as chromium.

Although not illustrated in the drawing, a protective layer may bedisposed on the black matrix BM. More specifically, the protective layermay be disposed between the black matrix BM and the first filter 220 todescribed later. The protective layer can prevent the black matrix BMfrom being damaged or corroded during the process of manufacturing theupper display panel 200. The material of the protective layer is notparticularly limited. However, the protective layer may include aninorganic insulating material such as silicon nitride or silicon oxide.The protective layer can be omitted.

Although not illustrated in the drawing, the black matrix BM can also bedisposed in the lower display panel 100. When the black matrix BM isdisposed in the lower display panel 100, it may be located between thefirst insulating layer 130 and the lower alignment film 140 in anembodiment. The black matrix BM disposed in the lower display panel 100can prevent light scattered by the light transmission patterns TC fromentering the wavelength conversion patterns WC, thereby suppressingcolor mixing.

In the present specification, when “a third element is disposed betweena first element and a second element,” it means that the position of thethird element varies depending on the arrangement of the first elementand the second element. That is, when the first element and the secondelement are arranged to overlap each other in the directionperpendicular to the lower substrate 110, the third element may beplaced to overlap each of the first element and the second element inthe direction perpendicular to the lower substrate 110. On the otherhand, when the first element and the second element are arranged tooverlap each other in a direction horizontal to the lower substrate 110,the third element may be placed to overlap each of the first element andthe second element in the direction horizontal to the lower substrate110. In the latter case, a second light transmission pattern TC2, whichwill be described later, is disposed between a first wavelengthconversion pattern WC1 and a second wavelength conversion pattern WC2which overlap each other in the direction horizontal to the lowersubstrate 110. This means that the second light transmission pattern TC2is placed to overlap each of the first wavelength conversion pattern WC1and the second wavelength conversion pattern WC2 in the directionhorizontal to the lower substrate 110.

The first filter 220 may be disposed on the black matrix BM. Morespecifically, the first filter 220 may be disposed on the black matrixBM to overlap the wavelength conversion patterns WC and the second lighttransmission pattern TC2. In addition, the first filter 220 may notoverlap with a first light transmission pattern TC1.

The first filter 220 may include an organic material havingphotosensitivity in an embodiment. The first filter 220 may have athickness of about 0.5 to 2 μm or about 0.5 to 1.5 μm in an embodiment.When having a thickness of 0.5 μm or more, the first filter 220 can havesufficient absorptive power for light of a specific wavelength band.When the thickness of the first filter 220 is 2 μm or less, the heightof a step formed by the first filter 220 can be minimized, and thedistance between the wavelength conversion patterns WC and the blackmatrix BM can be minimized. Accordingly, a color mixing defect can besuppressed.

The first filter 220 may be a cut-off filter that transmits light havinga specific wavelength band and blocks light having another specificwavelength band. This will be described later together with thewavelength conversion patterns WC by referring to FIG. 4.

The position of the filter 220 is not limited to that illustrated inFIG. 1 as long as the first filter 220 overlaps the wavelengthconversion patterns WC and the second light transmission pattern TC2.For example, the black matrix BM can be disposed on the first filter220. In an embodiment, the first filter 220 and the black matrix BM canbe disposed on the same layer.

The first low refractive layer 230 may be disposed on the first filter220. The first low refractive layer 230 may be disposed on the entiresurfaces of the black matrix BM and the first filter 220 in anembodiment. Accordingly, the first low refractive layer 230 may overlapeach of the first wavelength conversion pattern WC1, the secondwavelength conversion pattern WC2, the first light transmission patternTC1, and the second light transmission pattern TC2 in the directionperpendicular to the lower substrate 110.

The first low refractive layer 230 may be in contact with the firstwavelength conversion pattern WC1 and the second wavelength conversionpattern WC2. On the other hand, the first low refractive layer 230 isnot in contact with the first light transmission pattern TC1 and thesecond light transmission pattern TC2.

As used herein, the term ‘low refractive layer’ refers to a layer havinga relatively low refractive index as compared with an adjacent element.Therefore, the first low refractive layer 230 may have a lowerrefractive index than the wavelength conversion patterns WC to bedescribed later. For example, the first low refractive layer 230 mayhave a refractive index of about 1.1 to 1.4. On the other hand, thewavelength conversion patterns WC may have a refractive index of about1.8 to 1.9 in an embodiment.

The first low refractive layer 230 may reflect a portion of light, whichis emitted from the wavelength conversion patterns WC toward the uppersubstrate 210, back to the wavelength conversion patterns WC. That is,the first low refractive layer 230 may recycle at least a portion of thelight emitted from the wavelength conversion patterns WC toward theupper substrate 210, thereby improving the light output efficiency. Thiswill be described in more detail later with reference to FIG. 4.

The first low refractive layer 230 may include a resin and nanoparticles (such as zinc oxide (ZnO) or titanium dioxide (TiO₂))dispersed in the resin. However, the material of the first lowrefractive layer 230 is not particularly limited as long as therefractive index of the first low refractive layer 230 is lower thanthose of the wavelength conversion patterns WC. In an embodiment, thefirst low refractive layer 230 may include one of hollow silica, nanosilicate, and porogen.

The wavelength conversion patterns WC and the light transmissionpatterns TC will now be described in more detail with reference to FIG.3.

FIG. 3 is an enlarged view of an area A illustrated in FIG. 1. For easeof description, one first wavelength conversion material WC1 a, onesecond wavelength conversion material WC2 a, and one light scatteringmaterial TC1 a are illustrated in FIG. 3. In addition, the optical pathchange according to the refractive index is not taken into considerationin FIG. 3.

Referring to FIGS. 1 and 3, the wavelength conversion patterns WC may bedisposed on the first low refractive layer 230. The wavelengthconversion patterns WC may include a material capable of converting orshifting the wavelength band of light received from the outside.Accordingly, the wavelength conversion patterns WC can convert thedisplay color of light emitted to the outside into a display colordifferent from the display color of the light incident on the wavelengthconversion patterns WC. The wavelength conversion patterns WC mayinclude the first wavelength conversion pattern WC1 and the secondwavelength conversion pattern WC2.

The first wavelength conversion pattern WC1 may be disposed on the firstlow refractive layer 230 and may overlap the first subpixel electrodeSPE1 in the direction perpendicular to the lower substrate 110. Thesecond wavelength conversion pattern WC2 may be disposed on the firstlow refractive layer 230 and may overlap the second subpixel electrodeSPE2 in the direction perpendicular to the lower substrate 110.

More specifically, the first wavelength conversion pattern WC1 mayreceive the light L1 having the first wavelength band from the backlightunit 20, convert or shift the center wavelength of the light L1, andemit the light L1 having the converted or shifted center wavelength tothe outside. The light L1 whose center wavelength has been converted bythe first wavelength conversion pattern WC1 will be referred to as lightL2 having a second wavelength band.

The light L2 having the second wavelength band displays a second colordifferent from the first color. Here, the second color may be red havinga center wavelength of about 600 to 670 nm in an embodiment. That is,the light L2 having the second wavelength band is also defined as redlight whose center wavelength is in the range of about 600 to 670 nm.Therefore, the first wavelength conversion pattern WC1 can receive bluelight from the backlight unit 20 and convert the blue light into redlight.

The first wavelength conversion pattern WC1 will be described in moredetail below. The first wavelength conversion pattern WC1 may includethe first wavelength conversion material WC1 a and a first lighttransmitting resin WC1 b.

The first wavelength conversion material WC1 a may be a material thatconverts the light L1 having the first wavelength band into the light L2having the second wavelength band. The first wavelength conversionmaterial WC1 a may include first quantum dots in an embodiment. Theparticle size of the first quantum dots is not particularly limited aslong as the first wavelength conversion material WC1 a can convert thelight L1 having the first wavelength band into the light L2 having thesecond wavelength band.

The first quantum dots may have a core-shell structure. The core may bea semiconductor nanocrystalline material. In an embodiment, the core ofthe first quantum dots may be selected from a group II-VI compound, agroup III-V compound, a group IV-VI compound, a group IV element, agroup IV compound, and combinations of these materials.

The group II-VI compound may be selected from a binary compound selectedfrom CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS andmixtures of these materials; a ternary compound selected from CdSeS,CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS,CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe,MgZnS and mixtures of these materials; and a quaternary compoundselected from HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe,CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe and mixtures of these materials.

The group III-V compound may be selected from a binary compound selectedfrom GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSband mixtures of these materials; a ternary compound selected from GaNP,GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, A1PSb, InNP,InNAs, InNSb, InPAs, InPSb, GaAlNP and mixtures of these materials; anda quaternary compound selected from GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb,GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb,InAlPAs, InAlPSb and mixtures of these materials.

The group IV-VI compound may be selected from a binary compound selectedfrom SnS, SnSe, SnTe, PbS; PbSe, PbTe and mixtures of these materials; aternary compound selected from SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe,PbSTe, SnPbS, SnPbSe, SnPbSe and mixtures of these materials; and aquaternary compound selected from SnPbSSe, SnPbSeTe, SnPbSTe andmixtures of these materials. The group IV element may be selected fromSi, Ge, and a mixture of these materials. The group IV compound may be abinary compound selected from SiC, SiGe, and a mixture of thesematerials.

Here, the binary compound, the ternary compound, or the quaternarycompound may be present in particles at a uniform concentration or maybe present in the same particles at non-uniform concentrations. Inaddition, the binary compound, the ternary compound, or the quaternarycompound may have a core/shell structure in which one quantum dotsurrounds another quantum dot. The interface between the core and theshell may have a concentration gradient in which the concentration of anelement existing in the shell becomes lower toward the core.

The first wavelength conversion material WC1 a may be dispersed in anaturally coordinated form in the first light transmitting resin WC1 b.The first light transmitting resin WC1 b is not particularly limited aslong as it is a transparent medium that does not affect the wavelengthconversion performance of the first wavelength conversion material WC1 aand does not cause light absorption. For example, the first lighttransmitting resin WC1 b may include an organic material such as epoxyresin or acrylic resin.

The second wavelength conversion pattern WC2 may receive the light L1having the first wavelength band from the backlight unit 20, convert orshift the center wavelength of the light L1, and emit the light L1having the converted or shifted center wavelength to the outside. Thelight L1 whose center wavelength has been converted by the secondwavelength conversion pattern WC2 will be referred to as light L3 havinga third wavelength band. The light L3 having the third wavelength banddisplays a third color different from the first color and the secondcolor. Here, the third color may be green having a center wavelength ofabout 500 to 570 nm in an embodiment. That is, the light L3 having thethird wavelength band is also defined as green light whose centerwavelength is in the range of about 500 to 570 nm. Therefore, the secondwavelength conversion pattern WC2 can receive blue light from thebacklight unit 20 and convert the blue light into green light.

A sidewall of the second wavelength conversion pattern WC2 may be spacedapart from a sidewall of the first wavelength conversion pattern WC1.More specifically, the second light transmission pattern TC2 to bedescribed later is disposed between the sidewall of the secondwavelength conversion pattern WC2 and the sidewall of the firstwavelength conversion pattern WC1. Accordingly, light emitted from thefirst wavelength conversion material WC1 a in the first wavelengthconversion pattern WC1 and light emitted from the second wavelengthconversion material WC2 a in the second wavelength conversion patternWC2 can be prevented from being mixed with each other. This will bedescribed later.

The second wavelength conversion pattern WC2 will now be described inmore detail. The second wavelength conversion pattern WC2 may includethe second wavelength conversion material WC2 a and a second lighttransmitting resin WC2 b.

The second wavelength conversion material WC2 a may be a material thatconverts the light L1 having the first wavelength band into the light L3having the third wavelength band. The second wavelength conversionmaterial WC2 a may include second quantum dots in an embodiment. Theparticle size of the second quantum dots is not particularly limited aslong as the second wavelength conversion material WC2 a can convert thelight L1 having the first wavelength band into the light L3 having thethird wavelength band. In an embodiment, the core of the second quantumdots may be selected from a group II-VI compound, a group III-Vcompound, a group IV-IV compound, a group IV element, a group IVcompound, and combinations of these materials. Examples of each compoundor element are the same as those described above in relation to thefirst quantum dots and thus will not be described.

The second wavelength conversion material WC2 a may be dispersed in anaturally coordinated form in the second light transmitting resin WC2 b.The second light transmitting resin WC2 b is not particularly limited aslong as it is a transparent medium that does not affect the wavelengthconversion performance of the second wavelength conversion material WC2a and does not cause light absorption. For example, the second lighttransmitting resin WC2 b may include an organic material such as epoxyresin or acrylic resin.

The first and second quantum dots may have a full width at half maximum(FWHM) of an emission wavelength spectrum of about 45 nm or less,preferably about 40 nm or less, more preferably about 30 nm or less inan embodiment. In this range, the first and second quantum dots canimprove color purity or color reproducibility. In addition, since lightemitted through the first quantum dots and the second quantum dots isradiated in all directions, a wide viewing angle can be improved.

The size (e.g., particle size) of the first quantum dots may be greaterthan the size of the second quantum dots in an embodiment. For example,the size of the first quantum dots may be about 55 to 65 Å. Also, thesize of the second quantum dots may be about 40 to 50 Å Light emittedfrom each of the first and second quantum dots is radiated in variousdirections regardless of the incident angle of incident light.

In addition, each of the first and second quantum dots may be in theform of a spherical, pyramidal, multi-arm, or cubic nanoparticle,nanotube, nanowire, nanofiber, plate-like nanoparticle, or the like.

The light L2 having the second wavelength band emitted from the firstwavelength conversion pattern WC1 and the light L3 having the thirdwavelength band emitted from the second wavelength conversion patternWC2 may be in an unpolarized state through depolarization. As usedherein, ‘unpolarized light’ refers to light that is not composed only ofpolarization components in a specific direction, that is, light that isnot polarized only in a specific direction, in other words, light thatis composed of random polarization components. An example of theunpolarized light is natural light.

In an embodiment, the first wavelength conversion pattern WC1 and thesecond wavelength conversion pattern WC2 may include a phosphor, aquantum rod or a phosphor material, in addition to the first and secondquantum dots. Here, the phosphor may have a size of about 100 to 3000 nmin an embodiment. In addition, the phosphor may include a yellow, green,or red fluorescent material.

Before describing the light transmission patterns TC, the second filter240 will be described first.

The second filter 240 may be disposed on the first wavelength conversionpattern WC1 and the second wavelength conversion pattern WC2. The secondfilter 240 may cover outer surfaces of the first wavelength conversionpattern WC1 and the second wavelength conversion pattern WC2. Inaddition, the second filter 240 may be disposed under the lighttransmission patterns TC which will be described later. In other words,the second filter 240 may be formed in the upper display panel 200before the light transmission patterns TC.

The second filter 240 may be formed between the first wavelengthconversion pattern WC1, the second wavelength conversion pattern WC2 andthe light transmission patterns TC, so that the first wavelengthconversion pattern WC1, the second wavelength conversion pattern WC2,and the light transmission patterns TC do not contact each other.Accordingly, this can prevent the color mixing of light emitted from thefirst wavelength conversion pattern WC1, the second wavelengthconversion pattern WC2, and the light transmission patterns TC.

The second filter 240 may consist of a single layer or multiple layers.When consisting of multiple layers, the second filter 240 may include aSiNx layer and a SiOx layer stacked alternately in an embodiment. Thesecond filter 240 may have an average thickness of about 0.5 to 2 μm orabout 1 μm in an embodiment.

The second filter 240 may transmit light having a specific wavelengthband and reflect light having another specific wavelength band. Here,the center wavelength of the light reflected by the second filter 240may be longer than the center wavelength of the light transmittedthrough the second filter 240. That is, the second filter 240 maytransmit the light L1 having the first wavelength band and reflect thelight L2 having the second wavelength band and the light L3 having thethird wavelength band, wherein the center wavelength of the light L2having the second wavelength band and the center wavelength of the lightL3 having the third wavelength band are longer than the centerwavelength of the light L1 having the first wavelength band. Therefore,the second filter 240 may transmit blue light and reflect red light andgreen light.

The second filter 240 may reflect the light L2 having the secondwavelength band, which is emitted from the first wavelength conversionpattern WC1 toward the lower substrate 110, back toward the uppersubstrate 210, thereby improving the light output efficiency. Inaddition, the second filter 240 may transmit the light L1 having thefirst wavelength band provided from the backlight unit 20 but reflectlight whose center wavelength is longer than that of the light L1 havingthe first wavelength band. Therefore, the color purity of the light L1having the first wavelength band provided from the backlight unit 20 canbe improved. The path of light provided to the second filter 240 will bedescribed in more detail later with reference to FIG. 5.

The light transmission patterns TC will now be described. The lighttransmission patterns TC may be disposed on the second filter 240. Thelight transmission patterns TC may transmit light incident from theoutside without changing the color of the light.

More specifically, the light transmission patterns TC may include thefirst light transmission pattern TC1 and the second light transmissionpattern TC2.

The first light transmission pattern TC1 may be disposed on the secondfilter 240 and may overlap the third subpixel electrode SPE3 in thedirection perpendicular to the lower substrate 110. The second lighttransmission pattern TC2 may be disposed on the second filter 240 andmay be located between the first wavelength conversion pattern WC1 andthe second wavelength conversion pattern WC2. That is, the second lighttransmission pattern TC2 overlaps the first wavelength conversionpattern WC1 and the second wavelength conversion pattern WC2 in thedirection horizontal to the lower substrate 110.

More specifically, the first light transmission pattern TC1 may receivethe light L1 having the first wavelength band from the backlight unit 20and transmit the light L1 as it is without converting or shifting thecenter wavelength of the light L1. The first light transmission patternTC1 may not overlap the first filter 220. The first light transmissionpattern TC1 may include the light scattering material TC1 a and a thirdlight transmitting resin TC1 b.

The light scattering material TC1 a may be dispersed in the third lighttransmitting resin TC1 b to scatter light provided to the first lighttransmitting pattern TC1 and emit the scattered light to the outside.More specifically, the first light transmission pattern TC1 may scatterthe light L1 having the first wavelength band received from thebacklight unit 20 and emit the scattered light L1 to the outside. Thatis, the first light transmission pattern TC1 may receive blue light andtransmit the blue light as it is.

The light scattering material TC1 a may scatter incident light invarious directions regardless of the incident angle and emit thescattered light. Here, the emitted light may be in the unpolarized statethrough depolarization. That is, the light scattering material TC1 a mayscatter the light L1 having the first wavelength band, which is receivedfrom the backlight unit 20, in various directions regardless of theincident angle without converting the center wavelength of the light L1.Accordingly, the lateral visibility of the display device 1 according tothe embodiment can be improved.

The light scattering material TC1 a may be a material having a differentrefractive index from the third light transmitting resin TC1 b in anembodiment. In addition, the light scattering material TC1 a is notparticularly limited as long as it can scatter incident light. Forexample, the light scattering material TC1 a may be a metal oxide ororganic particles. The metal oxide may include titanium oxide (TiO₂),zirconium oxide (ZrO₂), aluminum oxide (Al₂O₃), indium oxide (In₂O₃),zinc oxide (ZnO), or tin oxide (SnO₂). The organic material may includeacrylic resin or urethane resin.

The third light transmitting resin TC1 b may be a transparent lighttransmitting resin in an embodiment. The third light transmitting resinTC1 b may be made of the same or different material from the first lighttransmitting resin WC1 b and the second light transmitting resin WC2 b.

The second light transmission pattern TC2 may be formed in the sameprocess as the first light transmission pattern TC1. In an embodiment,the second light transmission pattern TC2 may be formed at the same timeas the first light transmission pattern TC1 using the same mask.Accordingly, the second light transmission pattern TC2 may include thesame material as the first light transmission pattern TC1.

Since the second light transmission pattern TC2 is located between thefirst wavelength conversion pattern WC1 and the second wavelengthconversion pattern WC2, the height of a valley step formed between thefirst wavelength conversion pattern WC1 and the second wavelengthconversion pattern WC2 can be minimized. Accordingly, the flatness ofthe planarization layer 260 to be described later can be improved. Thiswill be described later with reference to FIGS. 6 and 7.

The second low refractive layer 250 may be disposed on the lighttransmission patterns TC and the second filter 240. The second lowrefractive layer 250 may be disposed on the entire surfaces of the lighttransmission patterns TC and the second filter 240 in an embodiment.Accordingly, the second low refractive layer 250 may overlap each of thefirst wavelength conversion pattern WC1, the second wavelengthconversion pattern WC2, the first light transmission pattern TC1, andthe second light transmission pattern TC2 in the direction perpendicularto the lower substrate 110.

The second low refractive layer 250 may not be in contact with the firstwavelength conversion pattern WC1 and the second wavelength conversionpattern WC2. On the other hand, the second low refractive layer 250 maybe in contact with the first light transmission pattern TC1 and thesecond light transmission pattern TC2. That is, unlike the first lowrefractive layer 230, the second low refractive layer 250 may notcontact the first wavelength conversion pattern WC1 and the secondwavelength conversion pattern WC2 but may contact the first lighttransmission pattern TC1 and the second light transmission pattern TC2.

The refractive index of the second low refractive layer 250 is notparticularly limited as long as it is lower than the refractive indicesof the wavelength conversion patterns WC. For example, the second lowrefractive layer 250 may have a refractive index of about 1.1 to 1.4. Inaddition, the refractive index of the first low refractive layer 230 andthe refractive index of the second low refractive layer 250 can be equalto or different from each other as long as they are lower than therefractive indices of the wavelength conversion patterns WC.

Of light emitted from the wavelength conversion patterns WC, lightemitted toward the lower substrate 110 may be reflected back toward thewavelength conversion patterns WC by the second low refractive layer250. That is, the second low refractive layer 250 can improve the lightoutput efficiency by recycling at least a portion of the light emittedfrom the wavelength conversion patterns WC.

The second low refractive layer 250 may include a resin and nanoparticles (such as zinc oxide (ZnO) or titanium dioxide (TiO₂))dispersed in the resin. However, the material of the second lowrefractive layer 250 is not particularly limited as long as therefractive index of the second low refractive layer 250 is lower thanthose of the wavelength conversion patterns WC. In an embodiment, thesecond low refractive layer 250 may include one of hollow silica, nanosilicate, and porogen. In an embodiment, the materials of the first lowrefractive layer 230 and the second low refractive layer 250 may be thesame. In an embodiment, the materials of the first low refractive layer230 and the second low refractive layer 250 may be different from eachother.

Referring again to FIG. 1, the planarization layer 260 may be disposedon the second low refractive layer 250. The planarization layer 260 mayprovide flatness to the second polarizing layer 280 which will bedescribed later. That is, when the first wavelength conversion patternWC1, the second wavelength conversion pattern WC2, the first lighttransmission pattern TC1 and the second light transmission pattern TC2are formed to different thicknesses in a process, the planarizationlayer 260 may make the heights of the above elements uniform.

The material of the planarization layer 260 is not particularly limitedas long as it has planarization characteristics. In an embodiment, theplanarization layer 260 may include an organic material. For example,the organic material may include cardo resin, polyimide resin, acrylicresin, siloxane resin, or silsesquioxane resin.

The second insulating layer 270 may be disposed on the planarizationlayer 260. The second insulating layer 270 may consist of at least onelayer having an insulating inorganic material. The insulating inorganicmaterial may include silicon nitride or silicon oxide in an embodiment.The second insulating layer 270 can prevent the planarization layer 260from being damaged in the process of forming the second polarizing layer280 which will be described later. In addition, the second insulatinglayer 270 can improve the adhesion of the second polarizing layer 280and can prevent the second polarizing layer 280 from being corroded ordamaged by air or moisture. The second insulating layer 270 can beomitted.

The second polarizing layer 280 may be disposed on the second insulatinglayer 270. The second polarizing layer 280 may be a wire grid polarizerin an embodiment. The second polarizing layer 280 will hereinafter bedescribed as a wire grid polarizer.

The second polarizing layer 280 may include a plurality of wire gridpatterns. In an embodiment, the wire grid patterns may include aconductive material through which a current flows. Here, the conductivematerial may include a metal such as aluminum (Al), silver (Ag), gold(Au), copper (Cu), or nickel (Ni) in an embodiment. In addition, theconductive material may further include titanium (Ti) or molybdenum(Mo). In an embodiment, the wire grid patterns may be a stackedstructure of at least two pattern layers.

For example, when light provided to the second polarizing layer 280passes through the second polarizing layer 280, components parallel tothe second polarizing layer 280 may be absorbed or reflected, andcomponents perpendicular to the second polarizing layer 280 may betransmitted to form polarized light. The second polarizing layer 280 maybe formed by a method such as nanoimprinting in an embodiment.

A capping layer 281 may be disposed on the second polarizing layer 280.The capping layer 281 may be disposed directly on the wire grid patternsto cover and protect the wire grid patterns. The capping layer 281 canprevent the second polarizing layer 280 from being damaged or corrodedby penetration of air or moisture. The capping layer 281 may be made ofan inorganic insulating material such as silicon nitride or siliconoxide in an embodiment.

The common electrode CE may be disposed on the capping layer 281. Atleast part of the common electrode CE may overlap the first throughthird subpixel electrodes SPE1 through SPE3. The common electrode CE maybe in the form of a whole plate in an embodiment. In addition, thecommon electrode CE may include a plurality of slits. The commonelectrode CE may be a transparent electrode or a translucent electrodeor may be made of a reflective metal such as aluminum, silver, chromiumor an alloy of these materials. Here, the transparent electrode or thetranslucent electrode may include one or more of indium tin oxide (ITO),indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In₂O₃), indiumgallium oxide (IGO), and aluminum zinc oxide (AZO).

The upper alignment film 290 may be disposed on the common electrode CE.The upper alignment film 290 may induce the initial alignment of theliquid crystal molecules 310 in the liquid crystal layer 300. The upperalignment film 290 may include a polymer organic material having animide group in a repeating unit of a main chain in an embodiment.

Next, the liquid crystal layer 300 will be described. The liquid crystallayer 300 includes a plurality of initially aligned liquid crystalmolecules 310. The liquid crystal molecules 310 may have negativedielectric anisotropy and may be vertically aligned in the initialalignment state. The liquid crystal molecules 310 may have apredetermined pretilt angle in the initial alignment state. The initialalignment of the liquid crystal molecules 310 can be induced by thelower alignment film 140 and the upper alignment film 290. When anelectric field is formed between the lower display panel 100 and theupper display panel 200, the liquid crystal molecules 310 may be tiltedor rotated in a specific direction to change the polarization state oflight transmitted through the liquid crystal layer 300.

The path of light provided from the backlight unit 20 will now bedescribed based on the first wavelength conversion pattern WC1 byreferring to FIGS. 3 through 5. FIGS. 4A through 5B illustrate opticalpaths in the display device 1 according to the embodiment. For ease ofdescription, different paths of the light L1 having the first wavelengthband and different paths of the light L2 having the second wavelengthband are indicated by different reference numerals in FIGS. 4 and 5.

The path of light emitted toward the upper substrate 210 will first bedescribed again with reference to FIG. 3.

As described above, the light L1 having the first wavelength band isprovided to the second filter 240 that covers the first wavelengthconversion pattern WC1. The second filter 240 provides the receivedlight L1 having the first wavelength band to the first wavelengthconversion pattern WC1 by transmitting the light L1. The firstwavelength conversion material WC1 a of the first wavelength conversionpattern WC1 converts the light L1 having the first wavelength band intothe light L2 having the second wavelength band by shifting the centerwavelength of the light L1. The light L2 having the second wavelengthband is emitted toward the outside, that is, toward the upper substrate210.

Hereinafter, the path of light that fails to be emitted toward the uppersubstrate 210 will be described with reference to FIGS. 4 and 5.

Referring to FIG. 4A, light L1 a having the first wavelength band isconverted into the light L2 having the second wavelength band by thefirst wavelength conversion material WC1 a of the first wavelengthconverting pattern WC1. However, when the light L2 having the secondwavelength band is emitted toward the upper substrate 210, it can beprovided to the black matrix BM and absorbed by the black matrix BMwithout being emitted out of the upper display panel 200. This light isdefined as ineffective light NL that does not affect luminance. Theineffective light NL may be a factor that reduces the light outputefficiency.

In addition, although not illustrated in the drawing, the light L2having the second wavelength band can be totally reflected due to thedifference between the refractive index of the upper substrate 210 andthe refractive index of outside air. Accordingly, the light L2 havingthe second wavelength band can be incident on the wavelength conversionpatterns WC or the light transmission patterns TC of another pixel. Thelight incident on another pixel is defined as noise light. The noiselight can reduce color purity and cause deterioration of image quality.

The display device 1 according to the embodiment may include the firstlow refractive layer 230 disposed between the first wavelengthconversion pattern WC1 and the upper substrate 210. The first lowrefractive layer 230 has a lower refractive index than the firstwavelength conversion pattern WC1.

Since the refractive index of the first low refractive layer 230 islower than that of the first wavelength conversion pattern WC1 asdescribed above, when the incident angle of the light L2 having thesecond wavelength band illustrated in FIG. 4A is equal to or greaterthan a total reflection critical angle, the light L2 having the secondwavelength band is totally reflected toward the first wavelengthconversion pattern WC1 at a first interface B1 between the first lowrefractive layer 230 and the first wavelength conversion pattern WC1.Accordingly, the light L2 having the second wavelength band is incidenttoward the first wavelength conversion pattern WC1 again. The light L2re-incident toward the first wavelength conversion pattern WC1 isdefined as recycled light RL.

The recycled light RL can have an opportunity to be emitted toward theupper substrate 210 again by the second filter 240 or the second lowrefractive layer 250. That is, the first low refractive layer 230 canprevent the light L2 having the second wavelength band from becoming theineffective light NL or the noise light, thereby improving light outputefficiency, color purity, and display quality.

When the incident angle of the light L2 having the second wavelengthband illustrated in FIG. 4A is smaller than the total reflectioncritical angle, the incident angle of light incident from the uppersubstrate 210 to the outside air is reduced due to the first lowrefractive layer 230 formed between the first wavelength conversionpattern WC1 and the upper substrate 210 (in a case where the refractiveindex of the upper substrate 210 is higher than that of the first lowrefractive layer 230). Accordingly, the total reflection ratio of thelight incident from the upper substrate 210 to the outside air isreduced, and the light incident from the upper substrate 210 to theoutside air can be concentrated close to a direction perpendicular tothe upper substrate 210.

If the light incident from the upper substrate 210 to the outside air isincident again on the upper display panel 200 through total reflection,the re-incident light may be absorbed by the black matrix BM to becomethe ineffective light NL or may be provided to another pixel to becomethe noise light. This causes a reduction in the light output efficiencyand display quality of the display device 1.

However, since the display device 1 according to the embodiment includesthe first low refractive layer 230 between the upper substrate 210 andthe first wavelength conversion pattern WC1, the total reflection ratioof the light incident from the upper substrate 210 to the outside aircan be reduced, which, in turn, improves the light output efficiency andthe display quality.

Referring to FIG. 4B, light L1 b having the first wavelength band doesnot contact the first wavelength conversion material WC1 a of the firstwavelength conversion pattern WC1. Therefore, the center wavelength ofthe light L1 b having the first wavelength band may not be converted. Asdescribed above, the refractive index of the first low refractive layer230 is lower than that of the first wavelength conversion pattern WC1.Therefore, when the incident angle of the light L1 b which has the firstwavelength band and whose center wavelength has not been converted isequal to or greater than the total reflection critical angle, the firstlow refractive layer 230 may totally reflect the light L1 b, which hasthe first wavelength band and whose center wavelength has not beenconverted, into the first wavelength conversion pattern WC1 at a secondinterface B2.

Accordingly, the totally reflected light L1 b has an opportunity tocontact the first wavelength conversion material WC1 a within the firstwavelength conversion pattern WC1. That is, the first low refractivelayer 230 totally reflects the light L1 b, which has the firstwavelength band and whose center wavelength has not been converted, backinto the first wavelength conversion pattern WC1 in order to give anopportunity for the center wavelength of the light L1 b to be converted.As a result, the light output efficiency can be improved.

Next, referring to FIG. 4C, light L1 c having the first wavelength banddoes not contact the first wavelength conversion material WC1 a of thefirst wavelength conversion pattern WC1. Therefore, the centerwavelength of the light L1 c having the first wavelength band may not beconverted. Further, when the incident angle of the light L1 c having thefirst wavelength band is smaller than the total reflection criticalangle, the light L1 c may not be totally reflected at a third interfaceB3 between the first low refractive layer 230 and the first wavelengthconversion pattern WC1. In this case, the light L1 c having the firstwavelength band may be provided to the first filter 220.

The first filter 220 may block (filter) the light L1 c, which has thefirst wavelength band and whose center wavelength has not beenconverted, from being emitted to the outside of the upper substrate 210.That is, the first filter 220 can prevent the light L2 having the secondwavelength band and the light L1 having the first wavelength band, whichdisplay different colors, from being mixed with each other, therebyimproving color purity.

While a case where the first filter 220 blocks the light L1 having thefirst wavelength band has been described above, the wavelength bandblocked by the first filter 220 can vary according to the wavelengthband of light emitted from the backlight unit 20.

Next, the path of light emitted from the first wavelength conversionpattern WC1 toward the lower substrate 110 will be described withreference to FIG. 5.

Referring to FIG. 5A, some L2_a1 of the light L2 having the secondwavelength band may travel toward the lower substrate 110 without beingemitted toward the upper substrate 210. As described above, the secondfilter 240 may transmit the light L1 having the first wavelength bandand reflect the light L2 having the second wavelength band and the lightL3 having the third wavelength band, wherein the center wavelength ofthe light L2 having the second wavelength band and the center wavelengthof the light L3 having the third wavelength band are longer than thecenter wavelength of the light L1 having the first wavelength band. Inan embodiment, the second filter 240 may be a dichroic filter.

Therefore, the second filter 240 may reflect the light L2_a1 having thesecond wavelength band back to the upper substrate 210 at a firstinterface C1 between the first wavelength conversion pattern WC1 and thesecond filter 240. The light L2_a2 reflected by the second filter 240may enter the first wavelength conversion pattern WC1 and have anopportunity to be emitted toward the upper substrate 210.

While a case where the second filter 240 transmits the light L1 havingthe first wavelength band and reflects light having a wavelength bandwhose center wavelength is longer than the center wavelength of thelight L1 has been described above, the center wavelength band reflectedby the second filter 240 can vary according to the wavelength band oflight emitted from the backlight unit 20.

Referring to FIG. 5B, when the incident angle of light L1 d having thefirst wavelength band and not contacting the first wavelength conversionmaterial WC1 a is equal to or greater than the total reflection criticalangle, the light L1 d may be reflected by the second low refractivelayer 250 back to the first wavelength conversion pattern WC1. Thus, thelight L1 d incident on the first wavelength conversion pattern WC1 canhave an opportunity to contact the first wavelength conversion materialWC1 a within the first wavelength conversion pattern WC1 and anopportunity to be output again toward the upper substrate 210.

Here, the light L1 d having the first wavelength band illustrated inFIG. 5B may be, for example, the light L1 b input to the firstwavelength conversion pattern WC1 by the total reflection at the secondinterface B2 between the first wavelength conversion pattern WC1 and thefirst low refractive layer 320 in FIG. 4B.

Since the second filter 240 transmits the light L1 having the firstwavelength band as described above, the light L1 d having the firstwavelength band may be transmitted through the second filter 240 andprovided to the second low refractive layer 250 The refractive index ofthe second low refractive layer 250 is smaller than that of the firstwavelength conversion pattern WC1.

Therefore, when the incident angle of the light L1 d having the firstwavelength band and travelling toward the second low refractive layer250 is equal to or greater than the total reflection critical angle, thelight L1 d having the first wavelength band may be totally reflectedback into the first wavelength conversion pattern WC1 at an interface C2between the second filter 240 and the second low refractive layer 250.The light L1 d incident on the first wavelength conversion pattern WC1has an opportunity to contact the first wavelength conversion materialWC1 a within the first wavelength conversion pattern WC1 and anopportunity to be output toward the upper substrate 210 again.

That is, the second low refractive layer 250 totally reflects the lightL1 d, which has the first wavelength band and whose center wavelengthhas not been converted, back into the first wavelength conversionpattern WC1, thereby providing an opportunity for the center wavelengthof the light L1 d to be converted. As a result, the light outputefficiency can be improved.

Although not illustrated in the drawing, of the light L2 which has thesecond wavelength band and whose center wavelength has been converted bythe first wavelength conversion material WC1 a, a portion of lightdirected toward the lower substrate 110 may travel toward the secondrefractive layer 250 without being reflected by the second filter 240.In this case, the second low refractive layer 250 may totally reflectthe received light L2 having the second wavelength band back into thefirst wavelength conversion pattern WC1. That is, since the light L2having the second wavelength band is given an opportunity to be emittedtoward the upper substrate 210 again, the light output efficiency can beimproved.

Next, the flatness of the planarization layer 260 will be described inmore detail with reference to FIGS. 6A and 6B and 7.

FIG. 6A illustrates the area A of FIG. 1 turned over. FIG. 6Billustrates the area A of FIG. 1 turned over in a case where the secondlight transmission pattern TC2 is omitted. FIG. 7 illustrates theflatness of the planarization layer 260 among the elements of thedisplay device 1 according to the embodiment.

Referring to FIG. 6A, the planarization layer 260 includes a firstsurface 260 a which contacts the second insulating layer 270 (seeFIG. 1) and a second surface 260 b which contacts the second lowrefractive layer 250. The second low refractive layer 250 includes afirst surface 250 a which contacts the second surface 260 b of theplanarization layer 260 and a second surface 250 b which is opposite thefirst surface 250 a.

The second light transmission pattern TC2 is disposed in a valley areaGA between the first wavelength conversion pattern WC1 and the secondwavelength conversion pattern WC2. Thus, the second light transmissionpattern TC2 can provide flatness to the second low refractive layer 250.That is, the second light transmission pattern TC2 is formed to fill thevalley area GA between the first wavelength conversion pattern WC1 andthe second wavelength conversion pattern WC2, thereby minimizing a stepheight h1 of the second surface 250 b of the second low refractive layer250. As the step height h1 of the second surface 250 b of the second lowrefractive layer 250 is minimized, a step height h2 of the first surface250 a of the second low refractive layer 250 may also be minimized.Here, the step height of a specific surface refers to a heightdifference between a lowest part and a highest part of the specificsurface.

As the step heights h2 and h1 of the first surface 250 a and the secondsurface 250 b of the second low refractive layer 250 are minimized, thethickness of the second low refractive layer 250 for step heightcompensation may also be reduced. In an embodiment, the second lowrefractive layer 250 may be formed to a thickness de2 of about 1 μm orless. The reduction in the thickness de2 of the second low refractivelayer 250 can reduce the cost of forming the second low refractive layer250 and reduce the occurrence of cracks.

Furthermore, when the step height h2 of the first surface 250 a of thesecond low refractive layer 250 is minimized, the step height of thefirst surface 260 a of the planarization layer 260 disposed on thesecond low refractive layer 250 may also be minimized. In an embodiment,the first surface 260 a of the planarization layer 260 may have a stepheight h3 of about 0 to 40 in. Thus, the flatness of the planarizationlayer 260 can be sufficiently secured. In addition, as the step heightof the planarization layer 260 is minimized, a thickness de3 of theplanarization layer 260 necessary for step height compensation may alsobe reduced. In an embodiment, the thickness de3 of the planarizationlayer 260 may be about 2 to 3 μm. The reduction in the thickness de3 ofthe planarization layer 260 can reduce the cost of forming theplanarization layer 260 and prevent the warpage of the planarizationlayer 260.

FIG. 6A will be described in more detail through comparison with FIG.6B. For ease of description, the same reference numerals as those ofFIG. 6A will be used in FIG. 6B.

When the second light transmission pattern TC2 is absent as illustratedin FIG. 6B, the second low refractive layer 250 is formed to fill thevalley area GB between the first wavelength conversion pattern WC1 andthe second wavelength conversion pattern WC2. Here, the absence of thesecond light transmission pattern TC2 denotes that the first lighttransmission pattern TC1 is disposed under the second filter 240.

Therefore, a step height h4 of the first surface 250 a of the second lowrefractive layer 250 is increased by the height of the valley step.Accordingly, the step height h4 of the first surface 250 a of the secondlow refractive layer 250 illustrated in FIG. 6B is greater than the stepheight h2 of the first surface 250 a of the second low refractive layer250 illustrated in FIG. 6A. Therefore, in order to compensate for thestep height h4, the second low refractive layer 250 illustrated in FIG.6B should have a large thickness de4. The increase in the thickness de4of the second low refractive layer 250 causes the occurrence of cracksin the second low refractive layer 250 and an increase in the cost offorming the second low refractive layer 250. In an embodiment, thethickness de4 of the second low refractive layer 250 illustrated in FIG.6B may be about 3 to 4 μm.

In addition, the step height h4 of the first surface 250 a of the secondlow refractive layer 250 affects the step height h5 of the first surface260 a of the planarization layer 260. Since the planarization layer 260is formed on the second low refractive layer 250, a thickness de5 of theplanarization layer 260 should be large enough to compensate for thestep height h4 of the first surface 250 a of the second low refractivelayer 250. In an embodiment, the thickness de5 of the planarizationlayer 260 illustrated in FIG. 6B may be about 4 to 6 μm. The increase inthe thickness de5 of the planarization layer 260 causes an increase inthe overall thickness of the upper display panel 200 and the warpage ofthe planarization layer 260.

That is, the display device 1 according to the embodiment can provideflatness to the second low refractive layer 250 and the planarizationlayer 260 by including the second light transmission pattern TC2.Therefore, the occurrence of cracks in the second low refractive layer250 and the warpage of the planarization layer 260 can be prevented.Furthermore, the cost of forming the second low refractive layer 250 andthe planarization layer 260 can be reduced.

A thickness de1 of the first low refractive layer 230 illustrated inFIG. 6A is not particularly limited. However, in an embodiment, thethickness de1 of the first low refractive layer 230 may be set to about1 μm or less in consideration of crack occurrence and cost. That is, thethickness de1 of the first low refractive layer 230 may be the same asthe thickness de2 of the second low refractive layer 250. However, theinventive concept is not limited to this case, and the thickness de1 ofthe first low refractive layer 230 can also be different from thethickness de2 of the second low refractive layer 250.

FIG. 7 illustrates the flatness of the first surface 260 a of theplanarization layer 260 among the elements of the display device 1according to the embodiment.

Referring to FIG. 7, the first surface 260 a of the planarization layer260 may have different step heights at different positions D1 through D9in consideration of process conditions and the positional relationshipwith other elements. However, since the display device 1 according tothe embodiment includes the second light transmission pattern TC2located between the first wavelength conversion pattern WC1 and thesecond wavelength conversion pattern WC2, the step heights of the firstsurface 260 a of the planarization layer 260 can be minimized. In anembodiment, the step heights at the positions D1 through D9 on the firstsurface 260 a of the planarization layer 260 may all be in the range of0 to 40 nm.

The color mixing reducing effect of the display device 1 according tothe embodiment will now be described with reference to FIG. 8.

As described above, the display device 1 according to the embodimentincludes the first low refractive layer 230 to prevent light emittedtoward the upper substrate 210 from being totally reflected to anadjacent pixel. Therefore, color mixing can be prevented.

The color mixing can also be suppressed by the second light transmissionpattern TC2.

FIG. 8 is a view for explaining the color mixing reducing effect of thedisplay device 1 according to the embodiment.

Referring to FIG. 8, the display device 1 according to the embodimentincludes the second light transmission pattern TC2 disposed between thefirst wavelength conversion pattern WCT and the second wavelengthconversion pattern WC2. The light L2 having the second wavelength bandscattered by the first wavelength conversion pattern WC1 may not enteran adjacent wavelength conversion pattern or an adjacent lighttransmission pattern due to the second filter 240. In some cases,however, the light L2 having the second wavelength band scattered by thefirst wavelength conversion pattern WC1 can transmit through the secondfilter 240 to enter the adjacent second wavelength conversion patternWC2.

Here, the second light transmission pattern TC2 disposed between thefirst wavelength conversion pattern WC1 and the second wavelengthconversion pattern WC2 in the display device 1 according to theembodiment may block the light L2 having the second wavelength bandscattered by the first wavelength conversion pattern WC1 from enteringthe second wavelength conversion pattern WC2. Thus, color mixing can beprevented.

The prevention of the color mixing can improve color reproducibility.This will now be described with reference to Table 1 below. Table 1compares the luminance of a conventional display device with the colorreproducibility of the display device 1 according to the embodiment. Thecolor reproducibility comparison is based on Commission Internationalede L'eclairage (CIE) 1931 and CIE 1976 established by the CIE. Theconventional display device in Table 1 refers to a display devicewithout the second light transmission pattern TC2 among display devicesdisplaying quantum dots.

Referring to Table 1, the color reproducibility of the display device 1according to the embodiment is better than that of the conventionaldisplay device by about 2.6%.

TABLE 1 Conventional Display Inventive Display Category Device DeviceDCI 1931 90.3 92.9 1976 94.8 96.1

Next, the optical characteristic effect of the display device 1according to the embodiment will be described with reference to Table 2below. Table 2 compares the luminance of a conventional display devicewith the luminance of the display device 1 according to the embodiment.The conventional display device in Table 2 refers to a display devicewithout a low refractive layer among display devices displaying quantumdots.

TABLE 2 Conventional Display Inventive Display Category Device DeviceLuminance (nit) 120 212 Color difference Δx 0.010, Δy 0.018 Δx 0.010, Δy0.020 0 degrees/60 degrees

Referring to Table 2, the luminance of the display device 1 according tothe embodiment is higher than the luminance of the conventional displaydevice by 77%. In addition, the display device 1 according to theembodiment has substantially the same color difference as theconventional display device. That is, since the display device 1according to the embodiment includes the first low refractive layer 230and the second low refractive layer 250, it can have improved luminancewhile maintaining the same color difference as the conventional displaydevice.

The luminance characteristics according to the refractive index valuesof the first low refractive layer 230 and the second low refractivelayer 250 included in the display device 1 according to an embodimentwill now be described with reference to Tables 3 and 4.

Table 3 below shows the luminance in a case where the first lowrefractive layer 230 and the second low refractive layer 250 have thesame refractive index value.

TABLE 3 Refractive index First low refractive layer 230 1.4 1.3 1.2Second low refractive layer 250 1.4 1.3 1.2 Average refractive index 1.41.3 1.2 Luminance 1.32 1.52 1.77

Referring to Table 3, in the case where the first low refractive layer230 and the second low refractive layer 250 have the same refractiveindex value, the luminance is highest when the average of the refractiveindex values of the first low refractive layer 230 and the second lowrefractive layer 250 is lowest.

Table 4 below shows the luminance in a case where the first lowrefractive layer 230 and the second low refractive layer 250 havedifferent refractive index values.

TABLE 4 Refractive index First low refractive layer 230 1.2 1.2 1.3Second low refractive layer 250 1.3 1.4 1.4 Difference in refractiveindex 0.1 0.2 0.1 Average refractive index 1.25 1.3 1.35 Luminance 1.591.44 1.38

Referring to Table 4, even in the case where the first and second lowrefractive layers 230 and 250 have different refractive index values,the luminance is highest when the average of the refractive index valuesof the first low refractive layer 230 and the second low refractivelayer 250 is lowest.

As is apparent from the above, the luminance is more affected by theaverage of the refractive index values of the first and second lowrefractive layers 230 and 250 than by the difference between therefractive index values. Accordingly, the display device 1 according tothe embodiment can improve the luminance by reducing the average of therefractive index values of the first low refractive layer 230 and thesecond low refractive layer 250.

FIGS. 9 through 14 illustrate other embodiments of the display device 1of FIG. 1. For simplicity, a description of elements and featuresidentical to those described above with reference to FIGS. 1 through 8will be omitted.

Referring to FIG. 9, a display device 2 according to an embodiment maynot include a second filter 240. That is, the display device 2 of FIG. 9is different from the display device 1 of FIG. 1 in that it does notinclude the second filter 240.

However, the display device 2 according to the embodiment may furtherinclude third insulating layer 295 in order to prevent a firstwavelength conversion pattern WC1, a second wavelength conversionpattern WC2, a first light transmission pattern TC1, and a second lighttransmission pattern TC2 from directly contacting each other. The thirdinsulating layer 295 may consist of at least one layer including aninorganic material in an embodiment. The inorganic material may includea silicon nitride (SiNx) layer and a silicon oxide (SiOx) layer in anembodiment. The thickness of the third insulating layer 295 is notlimited to that illustrated in FIG. 9 as long as the wavelengthconversion patterns WC and the light transmission patterns TC do notdirectly contact each other.

Even if the display device 2 according to the embodiment does notinclude the second filter 240, the light output efficiency can bemaintained because some of the light emitted from the first wavelengthconversion pattern WC1 can be input again into the first wavelengthconversion pattern WC1 by a second low refractive layer 250.

Referring to FIG. 10, a display device 3 according to an embodiment maynot include a first filter 220. That is, the display device 3 of FIG. 10is different from the display device 1 of FIG. 1 in that it does notinclude the first filter 220.

Even if the display device 3 according to the embodiment does notinclude the first filter 220, the light output efficiency can bemaintained because some of the light emitted from a first wavelengthconversion pattern WC1 can be input again into the first wavelengthconversion pattern WC1 by a first low refractive layer 230.

Although not illustrated in the drawing, the display device 3 accordingto the embodiment may also not include both the first filter 220 and asecond filter 240.

Referring to FIG. 11, a display device 4 according to an embodiment mayinclude a first inorganic layer 231 instead of a first low refractivelayer 230. That is, the display device 4 of FIG. 11 is different fromthe display device 1 of FIG. 1 in that the first low refractive layer230 is replaced with the first inorganic layer 231.

The first inorganic layer 231 may have a refractive index of about 1.3to 1.5 in an embodiment. If the refractive index condition is satisfied,the material of the first inorganic layer 231 is not particularlylimited. In an embodiment, the first inorganic layer 231 may include asilicon nitride (SiNx) layer or a silicon oxide (SiOx) layer and may beformed as a single layer or may be formed by stacking a plurality oflayers.

Referring to FIG. 12, a display device 5 according to an embodiment mayinclude a second inorganic layer 251 instead of a second low refractivelayer 250. That is, the display device 5 of FIG. 12 is different fromthe display device 1 of FIG. 1 in that the second low refractive layer250 is replaced with the second inorganic layer 251.

The second inorganic layer 251 may have a refractive index of about 1.3to 1.5 in an embodiment. If the refractive index condition is satisfied,the material of the second inorganic layer 251 is not particularlylimited. In an embodiment, the second inorganic layer 251 may include asilicon nitride (SiNx) layer or a silicon oxide (SiOx) layer and may beformed as a single layer or may be formed by stacking a plurality oflayers.

Although not illustrated in the drawing, both a first low refractivelayer 230 and the second low refractive layer 250 can be replaced with afirst inorganic layer 231 and the second inorganic layer 251,respectively. Here, the refractive indexes of the first inorganic layer231 and the second inorganic layer 251 are not necessarily the same, andthe materials of the first inorganic layer 231 and the second inorganiclayer 251 can be different from each other.

Referring to FIG. 13, a display device 6 according to an embodiment maynot include a first low refractive layer 230. That is, the displaydevice 6 of FIG. 13 is different from the display device 1 of FIG. 1. inthat it does not include the first low refractive layer 230.

Referring to FIG. 14, a display device 7 according to an embodiment maynot include a second low refractive layer 250. That is, the displaydevice 7 of FIG. 14 is different from the display device 1 of FIG. 1 inthat it does not include the second low refractive layer 250.

The relationship between the position of a low refractive layer andluminance will now be described in more detail with reference to FIG.15.

FIG. 15 is a graph illustrating the luminance according to the positionof a low refractive layer in a display device according to anembodiment. In FIG. 15, ref represents a case where no low refractivelayer is included, (a) represents a case where only a first lowrefractive layer is included, (b) represents a case where only a secondlow refractive layer is included, and (c) represents a case where boththe first low refractive layer and the second low refractive layer areincluded. In addition, p1 represents a case where the average refractiveindex is 1,2, p2 represents a case where the average refractive index is1.3, and p3 represents a case where the average refractive index is 1.4.

Referring to FIG. 15, assuming that the refractive indices are the same,the luminance is highest when both the first and second low refractivelayers 230 and 250 are included. In addition, assuming that the numberof refractive layers included is the same, the luminance is highest whenthe average refractive index is lowest, as described above.

Therefore, the display device according to the embodiment can improveluminance by including both the first low refractive layer 230 and thesecond low refractive layer 250 and minimizing the average of therefractive indices of the first low refractive layer 230 and the secondlow refractive layer 250. However, the refractive indices of lowrefractive layers and the positions and number of the low refractivelayers can be variously set in consideration of the relationship withother elements, the required luminance, and the production cost.

FIG. 16 illustrates an embodiment of the display device 1 of FIG. 1.

Referring to an area F of FIG. 16, a display device 8 according to anembodiment may include a second light transmission pattern TC2′ and afirst light transmission pattern TC1 having different thicknesses. Thatis, since the second light transmission pattern TC2′ is formed in anarrower area than the first light transmission pattern TC1, it may bethinner than the first light transmission pattern TC1. In other words,even if the first light transmission pattern TC1 and the second lighttransmission pattern TC2′ are simultaneously formed through the sameprocess, they do not necessarily have the same thickness.

Hereinafter, a method of manufacturing the upper display panel 200 amongthe elements of the display device 1 according to the embodiment of FIG.1 will be described with reference to FIGS. 17 through 22. FIGS. 17through 22 illustrate a method of manufacturing a display deviceaccording to an embodiment. For simplicity, a description of elementsand features identical to those described above with reference to FIGS.1 through 8 will be omitted.

Referring to FIG. 17, the black matrix BM and the first filter 220 areformed on the upper substrate 210. The black matrix 13119 may be formedon the upper substrate 210 to include a plurality of openings. The firstfilter 220 may be formed on the black matrix BM to vertically overlapthe first subpixel electrode SPE1 and the second subpixel electrode SPE2described above with reference to FIG. 1. That is, the first filter 220does not overlap the third subpixel electrode SPE3 to be describedlater.

In an embodiment, the first filter 220 may be formed by forming anorganic material having photosensitivity on the entire surfaces of theblack matrix BM and the upper substrate 210 and then patterning theorganic material such that the first filter 220 is located only in areasvertically overlapping the first sub pixel electrode SPE1 and the secondsub pixel electrode SPE2. The organic material having photosensitivitymay be a yellow photoresist in an embodiment. In an embodiment, thefirst filter 220 may be formed by depositing an inorganic material usinga method such as chemical vapor deposition. The first filter 220 may beformed as a single layer or may be formed by stacking a plurality oflayers. When the first filter 220 consists of a plurality of layers, thetransmission wavelength band and the blocking wavelength band of thefirst filter 220 can be controlled by adjusting the material, therefractive index, the deposition thickness, etc. of each layer.

Referring to FIG. 18, the first low refractive layer 230 is formed onthe first filter 220, the black matrix BM, and the upper substrate 210.The first low refractive layer 230 may be formed on the entire surfacesof the first filter 220, the black matrix BM and the upper substrate 210to vertically overlap all of the wavelength conversion patterns WC andthe light transmission patterns TC to be described later. The thicknessof the first low refractive layer 230 may be about 1 μm or less.

The material of the first low refractive layer 230 is not particularlylimited as long as the refractive index of the first low refractivelayer 230 is about 1.1 to 1.4. That is, the first low refractive layer230 may include a resin and nano particles (such as zinc oxide (ZnO) ortitanium dioxide (TiO₂)) dispersed in the resin. In an embodiment, thefirst low refractive layer 230 may include one of hollow silica, nanosilicate, and porogen. In addition, the first inorganic layer 231 can beformed instead of the first low refractive layer 230.

Next, referring to FIG. 19, the first wavelength conversion pattern WC1and the second wavelength conversion pattern WC2 are formed on the firstlow refractive layer 230. The formation order of the first wavelengthconversion pattern WC1 and the second wavelength conversion pattern WC2is not particularly limited.

More specifically, a material including a plurality of first quantumdots that convert blue light into red light is deposited on atransparent organic material or a transparent photoresist and thenpatterned to leave only an area overlapping the first subpixel electrodeSPE1 in the direction perpendicular to the lower substrate 110. As aresult, the first wavelength conversion pattern WC1 is formed.

In addition, a material including a plurality of second quantum dotsthat convert blue light into green light is deposited on a transparentorganic material or a transparent photoresist and then patterned toleave only an area overlapping the second subpixel electrode SPE2 in thedirection perpendicular to the lower substrate 110. As a result, thesecond wavelength conversion pattern WC2 is formed.

After the formation of the first wavelength conversion pattern WC1 andthe second wavelength conversion pattern WC2, the second filter 240 isformed on the first wavelength conversion pattern WC1 and the secondwavelength conversion pattern WC2. The second filter 240 may be formedas a single layer or may be formed by stacking a plurality of layers.When the second filter 240 consists of a plurality of layers, thetransmission wavelength band and the reflection wavelength band of thesecond filter 240 can be controlled by adjusting the material, therefractive index, the deposition thickness, etc. of each layer.

Next, referring to FIG. 20, the light transmission patterns TC includingthe first light transmission pattern TC1 and the second lighttransmission pattern TC2 are formed on the second filter 240. The lighttransmission patterns TC are formed by stacking a material including alight scattering material for dispersing incident light on a transparentorganic material or a transparent photoresist and then patterning thestacked material to leave an area overlapping the third subpixelelectrode SPE3 in the direction perpendicular to the lower substrate 110and an area located between the first wavelength conversion pattern WC1and the second wavelength conversion pattern WC2.

That is, the first light transmission pattern TC1 and the second lighttransmission pattern TC2 may be formed simultaneously through the samemask process in an embodiment. Accordingly, the first light transmissionpattern TC1 and the second light transmission pattern TC2 may be made ofthe same material. In an embodiment, each of the first lighttransmission pattern TC1 and the second light transmission pattern TC2may include the light scattering material TC1 a capable of scatteringlight and the third light transmitting resin TC1 b in which the lightscattering material TC1 a is coordinated.

Referring to FIG. 21, the second low refractive layer 250 is formed onthe light transmission patterns TC and the second filter 240. The secondlow refractive layer 250 may be formed on the entire surfaces of thelight transmission patterns TC and the second filter 240. The thicknessof the second low refractive layer 250 may be about 1 μm or less.

The material of the second low refractive layer 250 is not particularlylimited as long as the refractive index of the second low refractivelayer 250 is about 1.1 to 1.4. The refractive index of the second lowrefractive layer 250 may be the same as or different from that of thefirst low refractive layer 230. In addition, the material of the secondlow refractive layer 250 may be the same as or different from .hat ofthe first low refractive layer 230. For example, the second lowrefractive layer 250 may include a resin and nano particles (such aszinc oxide (ZnO) or titanium dioxide (TiO₂)) dispersed in the resin. Inan embodiment, the second low refractive layer 250 may include one ofhollow silica, nano silicate, and porogen. In addition, the secondinorganic layer 251 can be formed instead of the second low refractivelayer 250.

Since the second light transmission pattern TC2 provides flatness to thesecond low refractive layer 250, the step height of the second lowrefractive layer 250 can be minimized.

Next, the planarization layer 260 is formed on the second low refractivelayer 250. More specifically, the forming of the planarization layer 260may include applying a to planarizing material and curing theplanarizing material. The planarizing material may include an organicmaterial such as a thermosetting resin in an embodiment.

As described above, as the step height of the second low refractivelayer 250 is minimized, the step height of the planarization layer 260may also be minimized, thereby improving the flatness of theplanarization layer 260.

Next, referring to FIG. 22, the second insulating layer 270, the secondpolarizing layer 280, the capping layer 281, the common electrode CE,and the upper alignment film 290 are formed on the planarization layer260. Here, since the flatness of the planarization layer 260 has beenimproved, a plurality of wire grid patterns included in the secondpolarizing layer 280 can be formed uniformly.

According to embodiments, the light output efficiency can be improveddue to the presence of a low refractive layer.

In addition, since a light transmission pattern is placed in a valleyarea between wavelength conversion patterns, flatness can be given tothe low refractive layer and a planarization layer.

Since the thickness of the low refractive layer is minimized, theoccurrence of cracks can be reduced, and the cost of forming the lowrefractive layer can be reduced.

Also, since the thickness of the planarization layer is minimized, thewarpage of the planarization layer can be prevented.

Although certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the inventive concept is not limitedto such embodiments, but rather to the broader scope of the presentedclaims and various obvious modifications and equivalent arrangements.

What is claimed is:
 1. A method of manufacturing a display device, themethod comprising: forming a first low refractive layer on a substrate;forming wavelength conversion patterns, which comprise a firstwavelength conversion pattern converting light having a first wavelengthband into light having a second wavelength band and a second wavelengthconversion pattern converting the light having the first wavelength bandinto light having a third wavelength band, on the first low refractivelayer; forming light transmission patterns which comprise a first lighttransmission pattern transmitting the light having the first wavelengthband and a second light transmission pattern disposed between the firstwavelength conversion pattern and the second wavelength conversionpattern; and forming a second low refractive layer on the wavelengthconversion patterns and the light transmission patterns, whereinrefractive indices of the first low refractive layer and the second lowrefractive layer are lower than those of the wavelength conversionpatterns.
 2. The method of claim 1, further comprising forming a firstfilter which is disposed between the first low refractive layer and thewavelength conversion patterns.
 3. The method of claim 2, wherein thefirst filter blocks the light having the first wavelength band andtransmits the light having the second wavelength band and the lighthaving the third wavelength band.
 4. The method of claim 1, furthercomprising forming a second filter which is disposed between thewavelength conversion patterns and the light transmission patterns. 5.The method of claim 4, wherein the second filter transmits the lighthaving the first wavelength band and reflects the light having thesecond wavelength band and the light having the third wavelength band.6. The method of claim 1, wherein at least one of the first lowrefractive layer and the second low refractive layer has a refractiveindex of 1.1 to 1.4.
 7. The method of claim 1, wherein at least one ofthe first low refractive layer and the second low refractive layercomprises one of zinc oxide, titanium dioxide, hollow silica, nanosilicate, and porogen.